When I take the key out of the ignition, the mini goes into sleep mode like it should. everything powers down like it should. If I start the car again within 15 mins or so, everything works just fine... but when i leave it for a while, anything over 20 mins or so, it completely cuts power, and the mini starts up fresh when i start the car again. how can I keep the 1900 from cutting the power!? thanks